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Sizing and bulking

Fill the house Episode 4 Episode 6 5 min read

The short version

Once a fruit, pod, grain or tuber has made its cells, it grows mostly by filling them. That’s sizing, or bulking in a tuber or a root, and it’s where the tonnes come from. It’s potassium’s time, once the foundation’s in. But most crops add few cells by now, and size put on with water and potassium alone grows fast and fragile.

From pea-sized on its stolon to full size. Bulking mostly fills the cells each tuber made early on.

The same cells, filled

Steve’s fundamentals come in the same order in every crop: cell division, then sizing or bulking, then maturity. Once a fruit, a pod, a grain or a tuber has made its cells, it grows mostly by filling them. In fruit that’s sizing. In a tuber or a root it’s bulking, and in a pod or a grain it’s filling. It’s the same job, and it’s where the tonnes come from.

Sizing adds few cells in most crops. The count is largely settled in the cell division window, so a crop mostly fills the cells it made. A few, like avocados and potatoes, keep adding some, more slowly. With fewer cells, each cell has to stretch to make the same size. The fruit can still size up, but it’s softer, and it bruises and stores less well.

sugar, from the leaves. potassium. a cell, filled with starch.

  • A small young potato cut in half, on the end of its white stolon: moist cream-white flesh inside a thin buff skin.

    Young

    a potato tuber, cut open, and its cells magnified

    small, and packed with small cells: most of its cells are made

  • The same potato at bulking, cut in half: more than twice as wide, with the same cream-white flesh and thin skin.

    Bulked

    the same tuber, and the same cells magnified

    more than twice as wide, mostly from those cells filling out

Bulking mostly fills the cells a tuber made while it was young, though it keeps adding a few. That’s where the tonnes come from. An illustration, simplified.

Earn the right

Sizing is potassium’s time. Potassium helps move sugar from the leaves into the fruit, the tubers and the grain, and that sugar, with water, is what fills them. A tuber or a grain stores the sugar as starch. But Steve’s rule is to earn the right to use it. Build the foundation, build the house, then fill it with potassium. Bring it in when the crop needs it for filling, not before. If potassium goes on early, through cell division, it competes with the calcium the cells are being built from.

Calcium. Potassium. Sugar, from the leaves.

  • A young potato plant, its hill cut away: the old seed piece, fine roots, and stolon tips hooked over and swelling into small, round young tubers.

    The foundation

    a potato plant at tuber set

    calcium goes into the young tubers while their cells are made

  • The same potato plant at bulking, flowering above the hill: six to eight full-size, oval, buff-skinned potatoes on the ends of its stolons.

    Then fill it

    the same plant at bulking

    now potassium: it helps move the sugar in, and the tubers fill

  • The same young potato plant at tuber set.

    Instead, potassium early

    the same plant at tuber set, given potassium

    it competes with the calcium the young tubers’ cells are being built from

Earn the right to use potassium. Build the foundation while the cells are being made, then fill them with potassium when the crop needs it for filling. Put it on early, through cell division, and it competes with the calcium the cells are being built from. An illustration, simplified.

“Try and bulk up with potassium when it’s needed.”

— Steve, on sizing

Fast isn’t strong

Steve tells this one from a bean crop’s sap report. Calcium had dropped hard through cell division. His reading: these beans will size up fast, on the water and the potassium, but their structure and their resistance to disease will be fragile. The beans page has the whole story.

Keep the engine running

The sugar that fills a crop is made in its leaves. So sizing only goes as well as the leaves keep working. Keep them healthy and free of disease and pests, and keep the leaves’ engine running right through. If it stalls, the filling slows before the crop has filled what it made.

Sugar, from the leaves.

  • A potato plant at bulking, cut away below the ground: a full green leafy top with a few white flowers, and big oval potatoes on the ends of their stolons in red-brown soil.

    Leaves kept working

    potatoes at bulking

    the leaves keep making sugar, and the potatoes keep filling

  • The same potato plant, its leaves yellowed, browned and dying back, and below the ground the same potatoes, smaller.

    Leaves gone early

    the same crop, the same day

    less sugar comes down, and the potatoes stop filling, smaller than they’d have been

The sugar that fills a crop is made in its leaves. Keep them working right through sizing and the crop keeps filling. Lose them early, and it stops short. An illustration, simplified.

Water matters here too. A crop fills with water as well as sugar. Swings between wet and dry through sizing show up as uneven size, and in some crops as cracked fruit or misshapen tubers. A steady supply fills evenly.

Water, and the wet soil it leaves. A lot of water, all at once.

  • A potato plant at bulking, cut away below the ground: a full green leafy top with a few white flowers, and big oval potatoes on the ends of their stolons in red-brown soil.

    Steady water

    a potato plant, bulking

    the potatoes fill evenly

  • The same potato plant, its potatoes uneven: some small, some big, one knobbly with a second growth on its end, one pinched in the middle, one long and pointed.

    Swings, wet and dry

    the same plant

    uneven sizes, and misshapen potatoes

A crop fills with water as well as sugar. Swings between wet and dry through sizing show up as uneven size, and in a potato as misshapen tubers. A steady supply fills evenly. An illustration, simplified.

Size to the spec

Bigger isn’t always better. With a potato grower, the first thing Steve asks is what their market wants: the size, and how even. Then he works back from it. Filling past what the buyer pays for doesn’t pay, and an even crop in spec is worth more than a few big ones. It’s recoveries that get paid for, not the tonnes.

The size the buyer wants.

  • A mesh bag of washed potatoes, uneven: a few very big ones, two of them tipped out in front, among a few middling ones.

    A few big ones

    filled past the spec

    bigger isn’t always better: filling past what the buyer pays for doesn’t pay

  • A mesh bag of washed potatoes, every one about the same middling size, with a few tipped out in front.

    In spec

    even, and the size the buyer wants

    an even crop in spec is worth more than a few big ones

Bigger isn’t always better. Start from what the market wants: the size, and how even. Filling past what the buyer pays for doesn’t pay, and an even crop in spec is worth more than a few big ones. An illustration, simplified.

When it sizes, crop by crop

Where each crop in the program builder sizes, fills or bulks, and for how long. Each bar is a whole season, from sowing or planting to harvest, or a tree’s year. Build yours in the program builder.

  • Potatoes about 120 days

    Tuber bulking: about 6 weeks

  • Beans about 70 days

    Cell expansion and sizing: about 10 days

  • Carrots about 120 days

    Early bulking · Bulking: about 6 weeks

  • Onions about 180 days

    Bulb filling and maturation: about 9 weeks

  • Poppies about 140 days

    Capsule fill: about 4 weeks

  • Sweet corn about 90 days

    Kernel fill: about 18 days

  • Cotton about 180 days

    Boll fill: about 6 weeks

  • Wheat about 170 days

    Grain fill: about 5 weeks

  • Avocados a year

    Fruit growth: about 3 months

  • Apples a year

    Fruit sizing · Bulking to early ripening: about 11 weeks

Where it fits in a program

  • Have the foundation in first. Sizing fills the cells that cell division made.
  • Bring potassium in as the crop starts to fill: when it’s needed, not before.
  • Keep the leaves working and the water steady, right through.
  • Size to what the market pays for: even, and in spec.
  • Sap test as sizing starts, so you know the crop has what it needs to fill.